Organic Analysis

Question 1

What is the test for alcohols

Answer 1

Add acidified potassium dichromate, changing from orange to green

Question 2

What is the test for aldehydes

Answer 2

Tollens’ Reagent or Fehling’s Solution

Question 3

What is the test for alkenes

Answer 3

Bromine water, changing from orange to colourless

Question 4

What is the test for carboxylic acids

Answer 4

Add sodium carbonate, causing fizzing/effervescence

Question 5

Issues with CO2, methane and water and why

Answer 5

CO2, methane and water vapour contribute to global warming as the bonds vibrate and absorbs infrared radiation

Question 6

Describe the graph of this spectroscopy

Answer 6

Wavenumber on x-axis, transmittance on y-axis

Question 7

Explain the apparatus for a infrared spectroscopy

Answer 7

Infrared radiation is passed through a reference box and a sample box. The detector finds the difference in transmittance in each

Question 8

Test for sulphates

Answer 8

Acidify the sample and add barium chloride solution. White precipitate formed

Question 9

Test for halides

Answer 9

Add silver nitrate. White for chloride, cream for bromide, yellow for iodide

Question 10

Test for alkalis

Answer 10

Litmus paper

Question 11

Test for acids

Answer 11

Litmus paper, must react with Mg to produce bubbles

Question 12

Test for NH4+ ions

Answer 12

Add aqueous sodium hydroxide and warm the mixture, the gas produced turns damp, red litmus paper blue

Question 13

Test for hydroxide ions

Answer 13

Add an acid, should get warmer OR turns red litmus paper blue

Question 14

Test for carbonate ions

Answer 14

Acid is added, pass the gas produced through limewater, which turns from clear to cloudy

Question 15

Test for magnesium ions

Answer 15

React with sodium hydroxide, white precipitate formed

Question 16

Test for barium ions

Answer 16

React with sulphuric acid, white precipitate produced